1. Field of the Invention
The present invention relates generally to novel pharmaceutical compositions of matter comprising one or more non-steroidal anti-inflammatory drugs in combination with at least one skeletal muscle relaxant, and to methods of using said compositions in the treatment of a variety of skeletal muscle disorders including skeletal muscle spasms, certain orthopedic conditions, disk syndromes, low back pain and the like.
2. Description of the Prior Art
Centrally acting skeletal muscle relaxants are generally prescribed either as single agents or as components of combination products. The Food and Drug Administration has approved indications for these medications as adjuncts to rest and physical therapy for relief of acute, painful musculoskeletal problems. Clinically, the mild pain associated with the majority of cases of minor muscle strains and minor injuries is self limiting. Most patients usually respond rapidly to rest. An anti-inflammatory drug may be useful when there is considerable tissue damage and edema. On the other hand, severe musculoskeletal strains and sprains, trauma, and cervical or lumbar radiculopathy as a consequence of degenerative osteoarthritis, herniated disk, spondylitis or laminectomy, often cause moderate or severe and more chronic painful skeletal muscle spasm. The principal symptoms include local pain, tenderness on palpation, increased muscle consistency and limitation of motion. For these patients skeletal muscle relaxants alone or in combination with an analgesic are frequently prescribed. Results of some studies have suggested that a formulation of a muscle relaxant and an analgesic provides greater benefit in patients with acute musculoskeletal problems than similar doses of an analgesic alone.
Table I lists several commercial combinations available. A current commercial muscle relaxant formulation is Soma.RTM. Compound by Carter-Wallace, Inc. which contains 200 mg carisoprodol and 325 mg aspirin. Carisoprodol is a centrally-acting muscle relaxant that does not directly relax tense skeletal muscles in man. Aspirin is a conventional non-narcotic analgesic with anti-inflammatory and antipyretic activity. The most common adverse reactions associated with the use of aspirin in this product have been gastrointestinal, including nausea, vomiting, gastritis, occult bleeding, constipation and diarrhea. Allergic type reactions associated with aspirin may also involve the respiratory tract and skin.
Another commercial skeletal muscle relaxant formulation is Parafon Forte.RTM. by McNeil Pharmaceutical. Parafon Forte contains 250 mg chlorzoxazone and 300 mg acetaminophen. Chlorzoxazone is a centrally-acting agent which does not directly relax tense skeletal muscles in man. Acetaminophen, a nonsalicylate analgesic, is a conventional non-narcotic analgesic with anti-pyretic activity.
Robaxisal .RTM. by A.H. Robins Company, Inc. is another commercial muscle relaxant formulation which contains 400 mg methocarbamol and 325 mg aspirin. The mechanism of action of methocarbamol in humans has not been established, but may be due to general central nervous system depression. Methocarbamol does not directly relax tense skeletal muscles in can. Adverse reactions that have been associated with aspirin in this formulation include: nausea and other gastrointestinal discomfort, gastritis, gastric erosion, vomiting, constipation, diarrhea, angioedema, asthma, rash, pruritis and urticaria.
Norgesic.RTM. and Norgesic.RTM. Forte are commercial products by Riker Laboratories, Inc. that contain a muscle relaxant, aspirin and caffeine. The specific formulation for Norgesic is 25 mg orphenadrine citrate, 385 mg aspirin and 30 mg caffeine. Norgesic Forte contains 50 mg orphenadrine citrate, 770 mg aspirin and 60 mg caffeine. Orphenadrine citrate is 2-dimethylaminoethyl 2-methylbenzhydryl ether citrate. The common side effects and concerns associated with the use of aspirin occur with the use of Norgesic and Norgesic Forte as well.
TABLE I __________________________________________________________________________ Some Combination Products Containing a Skeletal Muscle Relaxant TYPICAL DOSAGE CONTENTS OF A SINGLE TABLET PRESENTED AS TRADENAME SKELETAL MUSCLE RELAXANT ADDITIONAL INGREDIENTS NO. OF TABLETS __________________________________________________________________________ SOMA COMPOUND Carisoprodol 200 mg aspirin 325 mg 1-2 SOMA COMPOUND Carisoprodol 200 mg aspirin 325 mg 1-2 WITH CODEINE codeine PO.sub.4 16 mg PARAFON FORTE Chlorzoxazone 250 mg acetaminophen 300 mg 1-2 ROBAXISAL Methocarbamol 400 mg aspirin 325 mg 2 NORGESIC Orphenadrine 25 mg aspirin 385 mg 1-2 Citrate caffeine 30 mg NORGESTIC FORTE Orphenadrine 50 mg aspirin 770 mg 1/2-1 Citrate __________________________________________________________________________
At the present time, one commercial product, Parafon Forte, a skeletal muscle relaxant formulation containing acetaminophen, will be the subject of a hearing granted by the Commissioner of Food and Drugs on a proposal to withdraw approval of its new drug application sometime in 1985. The Director of the Bureau of Drugs of the FDA in a notice published in the Federal Register, 1982, 47 F.R. 22599 concluded that he was unaware of any adequate and well-controlled clinical investigation conducted by experts qualified by scientific training and experience . . . [that ] demonstrates that effectiveness of Parafon Forte. The present position of the Commissioner of Food and Drugs is set forth below [Federal Register, 1984, 49(200): 48212-48214]:
Approval of this NDA will be withdrawn unless there exists substantial evidence that Parafon Forte has the clinical effect that it purports or is represented to have under the conditions of use prescribed, recommended, or suggested in its labeling . . . PA1 mephenesin PA1 mephenesin carbamate PA1 mephenesin acid succinate PA1 methocarbamol PA1 chlorphenesin carbamate PA1 mephenoxalone PA1 metaxalone PA1 meprobamate PA1 carisoprodol PA1 zoxazolamine PA1 chlorzoxazone PA1 chlordiazepoxide HCl PA1 diazepam PA1 analexin PA1 baclofen PA1 chlormezanone PA1 cyclobenzaprine HCl PA1 orphenadrine citrate
It should be noted that all of the previously described skeletal muscle relaxant/non-narcotic analgesic formulations include either aspirin or acetaminophen as the non-narcotic analgesic agent. However, a number of alternative non-narcotic agents offering a variety of advantages over these conventionally employed non-narcotic analgesic antipyretics have now been developed. These newer non-steriodal anti-inflammatory drugs are widely administered orally in the treatment of mild to severe pain, as well as for a variety of disorders including rheumatoid and osteoarthritis. Within this class of drugs, the compounds vary widely in their chemical structure and their biological profiles as analgesics, anti-inflammatory agents and antipyretic agents. The principal advantages of these new non-steroidal anti-inflammatory drugs include not only the clinically superior analgesic and anti-inflammatory activity of these agents compared to aspirin, acetaminophen or phenacetin, but also a lessening of the adverse side effects experienced with these conventional agents; more specifically, the gastrointestinal ulcerations and bleeding experienced with aspirin and the hepatic toxicity prevalent with the use of large doses of acetaminophen.
While aspirin and acetaminophen have been utilized in those previous compositions, it has not been heretofore proposed to use any of the newer non-steroidal anti-inflammatory drugs (i.e. excluding aspirin, acetaminophen and phenacetin) in combination with skeletal muscle relaxants to achieve more pain relief, a lesser incidence of side effects and thereby a more effective treatment of the musculoskeletal disorder.